The Card Game consists of the following three steps:
- The user has a set of cards: the name of each criterion is written on each card together with some other information. Therefore, we have n cards, n being the number of criteria of a family. The user also receives a set of latter will depend on the user’s needs.
- The user ranks these cards from the least important to the most important. So, the user rank in ascending order according to the importance he wants to ascribe to the criteria: the first criterion in the ranking is the least important and the last criterion in the ranking is the most important. According to the user’s point of view, if some criteria have the same importance (i.e., the same weight), he should build a subset of cards holding them together with a clip or a rubber band.
- The user has to think about the fact that the importance of two successive criteria in the ranking can be more or less close. The determination of the weights must consider this smaller or bigger difference in the importance of successive criteria. So, the user introduces white cards between two successive cards. The weight of each criterion (card) for the decision problem is defined from the closeness (more or less important) of two successive criteria in the ranking.
Finally, taking advantage of the rankings obtained with a series of standardizations, it is possible to obtain the weight of each criterion (card) for the decision problem considered.